Enjoy the hiking! Sounds lovely with the fall foliage and all...
As far as your sister, what she needs is inpatient drug treatment in a facility that does nothing else. Therapy is not the treament of choice for addiction, because it doesn't work. After inpatient treatment for addiction, the treatment is either halfway house for addicts and/or 12 step meetings in NA or AA. Then, its 12 step meetings for life.
As you may have figured out by now, this treatment stuff doesn't always 'work' and seems to require the coooperation of the addict (and even then, it often doesn't work, as in the case of my daughter who leaves treatment before done). It's not a very hopeful picture unfortunately. But I can tell you as a recoverying addict and also as a mom of a using addict, its just the only game in town.
So urge your sister to go into inpatient drug treatment and stop putting a bandaid on this (or maybe, just maybe she can try an NA meeting a day) by see a therapist.
As for yourself, well you're already taking care of you out in the great outdoors!